The life of Dorothy Day serves as a model of religious and spiritual development across the human life span. Her life as a journalist, pacifist, and reformer makes her a role model to many-her involvement in social issues stretched from the women's suffrage movement to the Vietnam War. She is best known as a cofounder of the Catholic Worker Movement. Born on November 8, 1897 in Brooklyn, New York, she was the third of John and Grace Satterlee Day's five children. The family moved often due to John Day's work as a journalist and experienced spells of both poverty and moderate affluence. As a teenager, Day often found herself wandering the poorer neighborhoods of Chicago and New York, discovering her compassion for the plight of the poor and beauty in the midst of urban desolation. An avid reader, Day fueled her growing social conscience with books such as Upton Sinclair's novel The Jungle. Along with social concerns, organized religion intrigued Day. She was fascinated by the piety and spiritual discipline she witnessed in neighbors and roommates. While she disagreed with Church doctrines supporting charity over justice, she felt drawn to the Catholic Church because of its connection to immigrants and the poor.

In 1914 Day began attending the University of Illinois in Urbana, supporting herself with scholarships, domestic labor, and freelance writing. Her social outlook continued in a radical direction, and she dropped out of college after only 2 years. Soon after, she moved to New York and found a job covering labor strikes and demonstrations as a reporter for The Call, a socialist paper. After several months, she moved on to writing for The Masses, a socialist journal that was shut down for sedition within a few months of her arrival.

As a young woman, Day lived what she called a bohemian-like existence: moving from city to city, writing for different papers, living among the poor, and associating with young radicals. Day participated in, as well as wrote about, demonstrations and rallies regarding social conditions. In 1917 she went to prison for protesting in front of the White House about the exclusion of women from voting and holding public office. While in prison, she participated in a hunger strike to bring attention to the inhumane treatment of prisoners. Day and her suffragette companions were eventually freed by order of President Woodrow Wilson. She was jailed several more times in her life for acts of civil disobedience, including refusing to take part in civil defense drills in the 1950s and participating in a banned picket line when she was 75 years old.

Day's first novel, The Eleventh Virgin, published in 1924, included autobiographical information about a love affair she had had that resulted in pregnancy and an abortion. In 1924, with the money she obtained by selling the movie rights to the novel, Day bought a beach house on Staten Island where she sought emotional healing. She lived there for several years with her common-law husband, Forster Batterham, until the birth of their daughter, Tamar Therese, in 1927. Batterham shared Day's radical social views but opposed marriage and religion. As Day blossomed as a mother and seriously pursued her attraction to Catholicism, her relationship with Forster suffered. After Day and their daughter were baptized in 1928, Batterham left the family permanently. So began Day's concerted effort to reconcile her radical social views with her Catholic faith.

Day and her daughter eventually moved to New York City, and it was there, in 1932, that she met Peter Maurin. A French peasant and former Christian Brother who found his way to the United States, Maurin encouraged Day to use her journalistic skills to publicize Catholic social teaching and promote social transformation through peaceful means. In 1933 the first edition of The Catholic Worker was circulated in New York City for a penny a copy. Within a year, the eight-page newspaper grew from 2,500 to 10,000 copies a month. Day was the principal writer and editor, with Maurin frequently submitting short poems on faith and justice called Easy Essays.

The paper criticized industrialism and the accepted social order, and encouraged readers to take action based on the works of mercy outlined in Jesus' Sermon on the Mount. With the Depression in full swing and vast numbers of people in dire poverty, Day soon opened her apartment to practice what The Catholic Worker preached. Thus was born the first house of hospitality. Under Day's direction, it welcomed all and sought only to serve, not to evangelize. Eventually more apartments and then houses were acquired; by 1936 there were over 30 Catholic Worker houses across the country. In 2003, there were 185 worldwide.

The Catholic Worker Movement that Day inspired is known for its strong commitments to living in solidarity with the poor, acting on behalf of justice and practicing pacifism. These positions have drawn both criticism and praise throughout the years. During her lifetime, Day spoke and acted on every major social issue, including the Spanish Civil War in 1926, the Civil Rights movement of the 1950s and 1960s, the Catholic Church's Second Vatican Council, the Vietnam War, and the United Farm Workers' strikes in California. In addition to her public expressions of faith and justice, Day nurtured a deep prayer life, spending hours pondering scripture and the lives of saints.

By the end of her life, Day was embraced by her adopted church, but her name continues to spark debate in both Catholic and secular circles alike. She continued to write for The Catholic Worker and live in a house of hospitality until her death in 1980 at the age of 83. In 2000 Day was recommended for canonization as a saint, a process that typically takes several years.